1. Field of the Invention
The present invention relates to transporting wind turbine blades. More particularly, the present invention relates to a system and method for transporting long airfoils via railroad using a weighted assembly that applies a lateral straightening force to a curved airfoil.
2. Description of the Related Art
Large-scale wind turbines are used to generate electrical power. Such wind turbines consist of a tall tower with a generator nacelle rotatably coupled about the top of tower's vertical axis. A rotor hub extends out a horizontal axis of the nacelle. Two or more turbine blades are connected to the rotor hub at right angles to the horizontal axis. During operation, prevailing winds cause the turbine blades to rotate about the rotor hub's horizontal axis. The rotational forces are coupled to a generator within the nacelle, which produces electricity. The nacelle rotates about the vertical axis of the tower to maintain the wind turbine blades in proper orientation with the prevailing winds.
The various components of a large-scale wind turbine may be manufactured at different geographic locations, and are then transported to the ultimate power generation site where they are assembled, erected, and placed into operation. Since the manufacturing operations may be spread across the world, transportation of the components to the generation site may utilize various modes of transportation, including ships, barges, trains and trucks. The various components are expensive to manufacture, and include fragile components that must be protected and handled properly during transportation. The wind turbine blades are frequently transported by rail during some portion of the transportation process.
The evolution of technology and the economies of scale have led to the development and deployment of large-scale wind turbines with larger and larger proportions. The power generation capacity of large-scale wind turbines is directly related to the length of the turbine blades, which define the swept area and power capacity of the turbine. The wind loading stresses involved during operation, and the need to keep the total mass of the turbine blades reasonably low, has lead engineers to design and build turbine blades as monocoque structures, typically employing composite materials. The lengths of wind turbine blades now exceed 180 feet, and the trend is for longer blades in the future. Transportation of long turbine blades presents significant challenges to transportation engineers, particularly in the case of railroads, where the railroad track clearance profile is tightly limited and where the trains must traverse curved sections and complex rail yards.
Another notable aspect of wind turbine blade design is the fact that the blades flex under wind loading, and thus bend backwardly from the wind. Since the blades sweep in front of the supporting tower assembly, the increased length has created an issue where the blades may be pushed into the tower and cause damage. Wind turbine blade designers have addressed this issue by building blades with a curved profile, which are curved toward the wind and away from the tower. While this has solved the basic problem at hand, it has created new challenges for the transportation process. This is particularly true for railway transport, where limited track clearance profiles will not allow a blade to extend beyond some reasonable clearance limits both laterally and vertically. Thus it can be appreciated that there is a need in the art for a system and method addressing the problems related to transportation of curved wind turbine blades as well as other long and curved airfoil devices via rail.